The transcriptional response to cadmium, organic hydroperoxide, singlet oxygen and UV-A mediated by the sigmaE-ChrR system in Caulobacter crescentus

• Published in: Molecular microbiology Vol. 72; no. 5; p. 1159
• Main Authors: Lourenço, Rogério F, Gomes, Suely L
• Format: Journal Article
• Language: English
• Published: England 01-06-2009
• Subjects: Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Cadmium - metabolism; Caulobacter crescentus - genetics; Caulobacter crescentus - metabolism; Caulobacter crescentus - radiation effects; Gene Deletion; Gene Expression Regulation, Bacterial; Hydrogen Peroxide - metabolism; Mutagenesis, Site-Directed; Oligonucleotide Array Sequence Analysis; Oxidative Stress; RNA, Bacterial - genetics; Sigma Factor - metabolism; Singlet Oxygen - metabolism; Transcription, Genetic; Ultraviolet Rays
• ISSN: 1365-2958
• DOI: 10.1111/j.1365-2958.2009.06714.x

Caulobacter crescentussigma(E) belongs to the ECF (extracytoplasmic function) subfamily of RNA polymerase sigma factors, whose members regulate gene expression in response to distinct environmental stresses. During physiological growth conditions, data indicate that sigma(E) is maintained in reduced levels due to the action of ChrR, a negative regulator of rpoE gene expression and function. However, once bacterial cells are exposed to cadmium, organic hydroperoxide, singlet oxygen or UV-A irradiation, transcription of rpoE is induced in a sigma(E)-dependent manner. Site-directed mutagenesis indicated that residue C188 in ChrR is critical for the cadmium response while residues H140 and H142 are required for the bacterial response to organic hydroperoxide, singlet oxygen and UV-A. Global transcriptional analysis showed that sigma(E) regulates genes involved in protecting cells against oxidative damages. A combination of transcriptional start site identification and promoter prediction revealed that some of these genes contain a putative sigma(E)-dependent motif in their upstream regions. Furthermore, deletion of rpoE and two sigma(E)-dependent genes (cfaS and hsp20) impairs Caulobacter survival when singlet oxygen is constantly generated in the cells.